From the moment Ron Shaoul took it upon himself to investigate the practice of reading on the toilet, scouring medical literature and turning up nothing of note as to its public health consequences, the situation became clear that here, on his hands, was a big job.

Shaoul's curiosity was driven by his work as a doctor specialising in paediatric gastroenterology. He mustered some colleagues, drew up a questionnaire and had hundreds of people of all shapes and sizes complete it. What resulted was perhaps the most scientific attempt yet to shine light on a habit that rustles unseen behind closed doors.

Shaoul, who published his study in 2009, lamented that toilet reading was woefully neglected by scientists, considering the habit probably dated back to the emergence of printed books. Writers, on the other hand, have shown no such aversion. For some, their authority on the matter has bordered on the connoisseur.

The anonymous author of The Life of St Gregory couldn't help but notice that the toilet of the middle ages, high up in a castle turret, offered the perfect solitude for "uninterrupted reading"; Lord Chesterfield too saluted the benefits, recounting the tale of a man who used his time wisely in the "necessary house" to work his way through Horace. This was but the beginning.

No writer owned the arena of toilet reading more than Henry Miller. He read truly great books on the lavatory, and maintained that some, Ulysses for instance, could not be fully appreciated elsewhere. The environment was one that enriched substantial works – extracted their flavour, as he put it – while lesser books and magazines suffered. He singled out Atlantic Monthly.

Miller went so far as to recommend toilets for individual authors. To enjoy Rabelais, he advised a plain country toilet, "a little outhouse in the corn patch, with a crescent sliver of light coming through the door". Better still, he said, take a friend along, to sit with you for half an hour of minor bliss.

From a medical standpoint, there are plenty of questions to ask of toilet reading. Most can be worded in vague, euphemistic terms that convey the gist without delving into coprological detail. Does reading material become irreversibly infused with nasty contaminants when carried into the toilet? How long can unpleasant microbes live on glossy magazine covers or, for that matter, the pages of a newspaper? And what does the straightforward act of reading on the toilet do for bowel movements?

Val Curtis, director of the Hygiene Centre at the London School of Hygiene and Tropical Medicine, is a self-confessed toilet reader. There is, she says, a theoretical risk. To be blunt, bugs in your poo can get on your hands, be transferred to your reading material, and on to the hands of some other unfortunate. That risk is quite slim though. As Curtis says, "we don't need to get anal about it".

"The important thing is to wash your hands with soap after using the loo to get the bugs off," Curtis says. This way, even if you flicked through a shit-smeared copy of the Metro left on the toilet floor at Reading station, washing your hands before leaving should keep you quite safe. Of course, if you ran your hands over the most soiled pages, picked your nose and rubbed your fingers in your eyes, you might well get an infection. For the determined, there is always a way.

Microbes don't fare too well on absorbent surfaces, and might survive only minutes on newspaper. But plastic book covers and those shiny, smooth surfaces of Kindles, iPhones and iPads are more accommodating, and it's likely bugs can live on those for hours. A recent study by Curtis suggests that in Britain one in six mobile phones is contaminated with faecal matter, largely because people fail to wash their hands after going to the toilet.

Curtis, who is writing a book on disgust, says evolution has honed our sense of infectious risk. Hence our revulsion of bodily fluids and all things excremental, particularly when they are other people's. But a squeamishness of reading in the toilet is probably our primitive selves making us over-sensitive. "Disgust helps us avoid the bugs that make us sick," she says, "but it evolved in ancient times. We now have this psychological tendency to over-detect contagion."

Shaoul, who works at the Bnai Zion Medical Centre in Haifa, Israel, agrees that there is little to fear from unpleasant bugs when reading in the toilet. Most people who indulge in the habit – and his questionnaire pointed to more men and more educated, white-collar workers – do so at home or at work with their own material, rather than in random excrement-spattered lavatories.

More interesting to Shaoul is whether the simple act of reading on the toilet has an impact on bowel movements. "We thought sitting and reading while you were on the toilet might be relaxing and make things go better," Shaoul says. "We thought we might cure the world of constipation with our research."

Shaoul cast his net wide. He received completed questionnaires from 499 men and women, aged 18 to over 65 – some unemployed or students, others builders and academics; some from rural villages, others from the city. More than half of the men (64%) and 41% of the women confessed to being regular toilet readers. More often than not, they described their reading material as "whatever is around". In practice, this usually meant newspapers.

It transpires that toilet readers spend more time on the loo and consider themselves less constipated than non-toilet readers, but other measures of their defecation habits show the two groups hardly differ. Shaoul's work hints that toilet readers suffer more haemorrhoids – something that made for cautionary news stories around the world – but the effect is neglible.

Finally, Shaoul concluded that reading on the toilet is widespread, alleviates boredom, and is ultimately harmless. This rings true to Curtis. "I always have New Scientist by the toilet. I use it as distraction therapy. I don't particularly want to think about crapping."